The present invention relates to a mass spectrometer and more particularly to the mass spectrometer having an ion sprayer which effectively forms concentrated ion beam.
In the general mass spectrometry for analyzing polar molecules dissolved in liquid, a combined liquid chromatography/mass spectrometry (herein after called LC/MS) with a sprayer is widely used. In such LC/MS, the liquid sample is nebulized and ionized simultaneously under an atmospheric pressure based on an electrospray method or a pneumatically assisted electrospray method, and the ionized polar molecules are sampled and introduced into the analyzing means in the mass spectrometer.
The sprayer in these LC/MS has a nozzle for ionizing the sample which consists of a first capillary tube and a second capillary tube outside of the first capillary tube. The liquid sample passes through the first capillary tube and is emitted out from an end of the first capillary tube and at the same time nebulizing gas is emitted out from an end space between the first capillary tube and a second capillary tube so as to nebulize the liquid sample as small droplets. As an end electrode having hole is obtained opposite to the end portion of the nozzle and a high voltage is applied between the nozzle and the counter electrode from the end of the nozzle, the nebulized sample compounds are ionized as many ions and these ions are moved towards the counter electrode. Some of the ions are passed through the hole of counter electrode so as to be sampled and be introduced to the analyzing means for sorting respective masses of the ions.
In the general LC/MS, the ions are dispersed in front of the electrode and a maximum portion of the ion density usually forms a ring on the electrode. Therefore, the hole of the electrode is disposed on the maximum portion in order to sample the ions. But, as the ions are sampled from the only one part of the ring of the ions, the sampling efficiency is not so high.
Examples of such conventional LC/MS relating the electrospray method or the pneumatically assisted electrospray method are disclosed as follows; (1) "Ion Spray Interface for Combined Liquid Chromatography/Atmospheric Pressure Ionization Mass Spectrometry", Analytical Chemistry, Vol. 59, No. 22, Nov. 15, 1987, pp. 2642-2646
(2) "Atmospheric Pressure Ionization Mass Spectrometry", Analytical Chemistry, Vol. 62, No. 13, Jul. 1, 1990, pp. 713A-725A